Urinals & Nitrogen Although ...

Urinals & Nitrogen

Although you may have measured some nitrate in your toilet sample, the 9.3 grams of urea in a litre of urine will eventually be broken down by bacteria into ammonia, with potential ammonia concentrations well in excess of 1000 mg/L.  Bacteria in the environment will then convert the ammonia to nitrate.

Biological treatment is possible but certainly not the practical or simple biological system that you are seeking.  First you need to break down the urea to ammonia.  Then you would need to convert the ammonia to nitrate (nitrification). and finally you need to convert the nitrate to nitrogen gas (denitrification).  Each of these stages requires a different group of bacteria and environmental conditions.  For denitrification you will also need to add a readily biodegradable carbon source.

Even to use the urine as a source of nitrogen for plant growth, bacteria first need to break down the urea and convert it to nitrate.

Instead of biological treatment, you could consider using zeolite.  The following link is to an article on using struvite crystallisation and adsorption to zeolite to recover nutrients from human urine collected from urine separating toilets  - using MgO to precipitate struvite and zeolite to adsorb ammonia.

http://www.ncbi.nlm.nih.gov/pubmed/15027655